Apparatus and method for forming an optical converter

ABSTRACT

An optical converter and method for making same is provided. In accordance with the method, the present invention provides an improved apparatus and methods for fabrication of an optical converter. In one aspect of the invention a method for forming an optical converter is provided. In accordance with this method at least two light guide ribbon structures are provided, with each light guide ribbon structure formed by the steps of roll molding a substrate having a pattern of channels with each channel extending from an input edge to an output edge of said substrate and forming light guides extending along each of the channels from the input edge to the output edge. The at least two light guide ribbon structures are assembled in a stacked arrangement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to the following commonly assigned U.S.patent application Ser. No. 10/314,843 entitled “Optical Computer FormedFrom Flexible Strips” and U.S. patent application Ser. No. 10/314,557entitled “An Apparatus and System For Forming a Fiber Optic Faceplate”both filed on Dec. 9, 2002.

FIELD OF THE INVENTION

This invention generally relates to fabrication of optical convertersfor use in imaging systems and more particularly relates to an apparatusand method for forming an optical converter on a substrate.

BACKGROUND OF THE INVENTION

One advantage of electronic display systems is the capability to displayan image in a variety of formats and sizes. There is particular interestin providing large scale displays, visible to thousands of viewers overconsiderable distance, such as would be useful for entertainment andadvertising. One known method for providing large-scale electronicdisplays is tiling, in which a matrix of smaller displays are linkedtogether to form a larger display surface.

Image-forming devices such as LCDs, matrixed LEDs, Organic LightEmitting Diodes (OLEDs), and Polymer Light Emitting Diodes (PLEDs)provide a two dimensional image in pixel form, with pixels familiarlyarranged in rows and columns. A recognized problem for displays usingthese components relates to inherent dimensional limitations of theelectronic image-forming components themselves. Size and packagingrequirements for these devices constrain their use in large-scaledisplay applications, requiring special methods and techniques for imageenlargement and tiling.

Optical converters, typically comprising arrays of optical fibers, havebeen recognized as a means for enlarging an electronically generatedimage in order to display the image in a larger format, such as fortiling applications. For example, U.S. Pat. No. 6,195,016 entitled FiberOptic Display System with Enhanced Light Efficiency, filed Feb. 27,2001, by Shankle et al. discloses an enlarged display using imagesprovided from conventional transparencies, visibly enlarged by means offiber optic light guides, each fiber painstakingly routed from the imageforming device to a display panel. Similarly U.S. Pat. No. 6,418,254entitled Fiber-Optic Display, filed Jul. 9, 2002, by Shikata et al.discloses a fiber optic display coupled with an image projector. U.S.Pat. No. 6,304,703 entitled Tiled Fiber Optic Display Apparatus, filedOct. 16, 2001, by Lowry discloses a tiling implementation using bundlesof optical fibers routed from image-forming components to a displayapparatus.

As an alternative to routing individual fibers, symmetrically fixedgroupings of optical fibers are preferred. For example, U.S. Pat. No.5,465,315 entitled Display Apparatus Having A Plurality of DisplayDevices filed Nov. 7, 1995 by Sakai et al. discloses a tiled displayemploying LCD devices, with images tiled on a display surface using afiber optic faceplate. Fiber optic faceplates have also been disclosedfor use in a number of other applications, such as U.S. Pat. No.5,572,034 entitled Fiber Optic Plates For Generating Seamless Images,filed Nov. 5, 1996 by Karellas which discloses tiling using fiber opticfaceplates in an X-ray imaging apparatus and U.S. Pat. No. 5,615,294entitled Apparatus For Collecting Light and It's Method of Manufacture,filed Mar. 25, 1997 by Castonguay which discloses use of a tapered fiberoptic faceplate in light-sensing instrumentation.

Fiber optic faceplates that are commercially available are well suitedfor many types of image-sensing and instrumentation purposes. However,the overall requirements for using fiber optic faceplates for electronicimage display are more demanding, particularly when used with LCD, LED,OLED, or PLED devices. In such a case, it is important to have precisepositioning of optical fibers at the input and output sides of a fiberoptic faceplate. That is, each pixel at the image-forming device has acorresponding fiber light guide within the fiber optic faceplate thatdirects light from that pixel to the output display surface. Thisrequirement necessitates custom design of a fiber optic faceplate forthe geometry of the image forming device itself (such as for an OLED,for example) and for the geometry of the display surface. It can beappreciated that tiling arrangements introduce even more complexity intothe faceplate fabrication problem. As a result, fiber optic faceplatessuitable for electronic image display continue to be costly anddifficult to fabricate. Solutions for fiber optic faceplate fabrication,such as those disclosed in International Application WO 02/39155 (Cryanet al.) can be highly dependent on accurate dimensions of the opticalfiber or of interstitial fillers used to provide a precise spacingbetween fibers.

One prior art approach for providing accurate positioning of opticalfibers in a fiber bundle is disclosed in U.S. Pat. No. 3,989,578entitled Apparatus For Manufacturing Optical Fiber Bundle, filed Nov. 2,1976, by Hashimoto, hereinafter termed the '578 patent. In the method ofthe '578 patent, directed to the manufacture of fiberscope apparatus,optical fiber is wound around a mandrel and aligned in guide frames toobtain precise positioning. In U.S. Pat. No. 5,938,812 entitled Methodfor Constructing A Coherent Imaging Bundle, filed Aug. 17, 1999 byHilton, Sr., hereinafter termed the '812 patent, a multilayer fiberoptic bundle is fabricated by winding a fiber optic strand around adrum, within a plastic channel. In U.S. Pat. No. 3,033,731 entitledMethod For The Manufacture Of Optical Image-Transfer Devices, filed Mar.6, 1958, by Cole, hereinafter termed the '731 patent, fiber is woundabout a mandrel to form rows, which can then be combined to build up afiber structure. Thus, it can be seen that a drum or mandrel, properlydimensioned, can be a suitable apparatus for positional arrangement ofoptical fibers in a bundle. However, neither the '578, '812, nor '731patents provide a suitable solution for optical fiber faceplatefabrication. The methods used in the above-mentioned patents positionfibers adjacently, so that the dimensions of the fiber itself determinecenter-to-center spacing of the fiber bundle. However, such methods arehighly dependent on the uniformity of fiber dimensions. In actualpractice, however, the actual dimensions of optical fiber can varywidely, even for the same type of fiber. Additional tolerance error isdue to winding tension differences as the fiber strands are wound aboutthe drum. More significantly, however, the methods of the '578, '812,and '731 patents do not provide a way to vary the center-to-centerdistances between fibers, both at input and at output ends of the fiberbundle. As is noted earlier, the capability for varying thecenter-to-center distance between fibers, lacking with the methods ofthe '578, '812, and '731 patents, is of paramount importance for displayimaging applications.

In an attempt to meet the requirements for variable center-to-centerspacing, U.S. Pat. No. 5,204,927 (Chin et al.), hereinafter termed the'927 patent, discloses the use of pairs of axially disposed spacer bars.The use of spacer bars allows a fiber optic bundle to have differentfiber spacing at input and output ends. Similarly, U.S. Pat. No.5,376,201 entitled Method of Manufacturing An Image MagnificationDevice, filed Dec. 27, 1994, by Kingstone hereinafter termed the '201patent, discloses the use of spacer guides in a rotating drumapplication for output fiber spacing, where the output spacer guides,added as each layer of fiber is formed, become part of the completedfiber bundle assembly.

While the '927 and '201 disclosures suggest helpful fabricationtechniques for fiber optic couplers, there is felt to be considerableroom for improvement. In particular, neither the '927 nor the '201disclosure are well suited to the requirements for accurate, high-speed,and inexpensive fabrication of fiber optic faceplates as the type ofoptical converter needed for electronic display imaging. With respect toboth '927 and '201 disclosures, curvature effects of the rotating drumconstrain the attainable size of a fiber optic faceplate built up inthis way. Continuous feeding of optical fiber is necessary, whichsuggests a substantial amount of waste with the '927 and '201 methods.The method of the '201 disclosure relies heavily on precisionmanufacture of grooved spacer components, incorporated into the body ofthe fiber faceplate itself, used to define the spacing of each outputrow and to set the spacing between rows. Moreover, new spacers arerequired to be accurately positioned as each row of fibers is wound.This adds cost and complexity to the fabrication process.

U.S. Patent Application Publication 2002/0168157 (Walker et al.)discloses a method for fabrication of a fiber optic faceplate made fromstacked sheets of optical fibers, where the sheets are formed usingco-extrusion of fiber optic material through a specially designed die.These flat sheet structures can be stacked and bonded together, eitherusing heat or some other means, to form a composite structure, which canbe up to a few meters in length, comprising parallel lengths of opticalfiber that extend down the length of the composite structure. Thiscomposite structure is then cross-sectioned to obtain individual fiberoptic faceplates of a selectable thickness. Although this methodprovides some advantages for mass manufacture of fiber optic faceplates,significant drawbacks remain. For example, the extrusion method of thePublication 2002/0168157 disclosure (the '157 disclosure) maintains aconsistent spacing between optical fibers as they are formed; thismethod is not designed to allow varying the spacing between opticalfibers at different points along their lengths. The optical fibers inthe faceplate obtained with this method have the same center-to-centerspacing throughout the structure. In order to obtain different effectivecenter-to-center spacing for a fiber optic faceplate, input side tooutput side, the method of the '157 disclosure requires sectioning thecomposite structure of bonded fibers at an oblique angle. This rigidlyconstrains the number of possible center-to-center spacing arrangementsthat can be obtained from any one production run. Using the method ofthe '157 disclosure has further disadvantages with respect to sizingconstraints. The maximum dimensions of a fiber optic faceplate using'157 disclosure techniques is rigidly determined by the width of anextrusion die; obtaining a larger width structure requires building alarger extrusion die and scaling up the supporting mechanicalsubsystems, at costs which could easily be prohibitive. Spacing betweenstacked sheets, in a direction orthogonal to the row direction, is noteasily varied using the methods of the '157 disclosure, limiting therange of spacing dimensions that can be obtained. Cross-sectionaldiameters of the component optical fibers cannot be reliably varied fromthe input side of the fiber optic faceplate to the output side.

As the above examples illustrate, conventional methods for formingoptical converters as fiber optic faceplates are based on varioustechniques such as assembling individual optical fibers into a faceplatestructure, characteristically using winding or stitching operations orextruding rows of optical fibers into sheets for stacking, bonding, andcross-sectioning. Given the difficulties, costs and limitations inherentwhen using optical fibers as light guides, it can be appreciated thatalternative methods for providing an optical converter at reduced costand having added flexibility would be beneficial.

Overall, it can be seen that there is a need for improved methods forfabrication of optical converters, particularly for electronic imagingapplications.

SUMMARY OF THE INVENTION

The present invention provides an improved apparatus and methods forfabrication of an optical converter. In one aspect of the invention amethod for forming an optical converter is provided. In accordance withthis method at least two light guide ribbon structures are provided,with each light guide ribbon structure formed by the steps of rollmolding a substrate having a pattern of channels with each channelextending from an input edge to an output edge of said substrate andforming light guides extending along each of the channels from the inputedge to the output edge. The at least two light guide ribbon structuresare assembled in a stacked arrangement.

In another aspect of the invention, a method is provided for forming anoptical converter. In accordance with the method a web of light guideribbon structures is formed by the steps of roll molding a web substratehaving a pattern of channels, each channel spaced apart from itsadjacent channel in accordance with a predefined pattern, and coating anoptical material into the channels on the web of substrate to form lightguides, and segmenting the web of light guide ribbon structures to formindividual light guide ribbon structures with each ribbon structurehaving an input edge and an output edge with light guides extendingtherebetween. The individual light guide ribbon structures are assembledin a stacked arrangement.

In still another aspect of the invention, a method is provided forforming an optical converter. In accordance with the method an initialweb layer of light guide ribbon structures is formed by the steps ofroll molding a web of substrate having a pattern of channels eachchannel spaced apart from its adjacent channel in accordance with apredefined pattern and coating an optical material into the channels onthe web of substrate to form light guides. At least one subsequent weblayer of light guide ribbon structure is formed on the initial web layerby the steps of roll molding a web of substrate on the initial web layerof light guide ribbon structures, with each subsequent layer having apattern of channels each channel spaced apart from its adjacent channelin accordance with a predefined pattern and coating an optical materialinto the channels on the web of substrate to form light guides andsegmenting the web of light guide ribbon structure to form an opticalconverter having an input edge and an output edge with an array ofstacked light guides extending therebetween.

In another aspect of the invention, an optical converter is provided.The optical converter has at least two light guide ribbon structuresassembled in a stacked arrangement with each light guide ribbonstructure formed by the steps of roll molding a substrate having apattern of channels with each channel extending from an input edge ofthe substrate to an output edge of said substrate and forming lightguides extending along each of the channels from the input edge to theoutput edge.

In still another aspect of the invention, an optical converter isprovided. The optical converter has individual light guide ribbonstructures assembled in a stacked arrangement with each light guideribbon structure formed by the steps of roll molding a web of substratehaving a pattern of channels each channel spaced apart from its adjacentchannel in accordance with a predefined pattern and coating an opticalmaterial into the channels on the web of substrate to form light guidesand segmenting the web of light guide ribbon structures to formindividual light guide ribbon structures with each ribbon structurehaving an input edge and an output edge with light guides extendingtherebetween.

In still another aspect of the invention, an optical converter isprovided. The optical converter has an input edge and an output edgewith an array of stacked light guides extending therebetween with theoptical converter having an initial web layer of light guide ribbonstructures formed by the steps of roll molding a web of substrate havinga pattern of channels each channel spaced apart from its adjacentchannel in accordance with a predefined pattern and coating an opticalmaterial into the channels on the web of substrate to form light guidesand at least one subsequent web layer of light guide ribbon structure onthe initial web layer formed by the steps of roll molding a web ofsubstrate on the initial web layer of light guide ribbon structures,with each subsequent layer having a pattern of channels, each channelspaced apart from its adjacent channel in accordance with a predefinedpattern, and coating an optical material into the channels on the web ofsubstrate to form light guides.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter of the present invention, itis believed that the invention will be better understood from thefollowing description when taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 shows a first embodiment of an extrusion roll molding apparatus;

FIG. 2 shows another embodiment of an extrusion roll molding apparatus;

FIG. 3 shows an example of a substrate;

FIG. 4 shows a cross section view of the example substrate of FIG. 3;

FIG. 5 shows a perspective view of a light guide ribbon structure of thepresent invention;

FIG. 6 is a perspective view showing a substrate fabricated withchannels for multiple light guide ribbon structures;

FIG. 7 is a perspective view showing a substrate fabricated withchannels for multiple light guide ribbon structures;

FIG. 8 is a perspective view showing individual light guide ribbonstructures separated from each other by being severed from the substrateof FIG. 6;

FIG. 9 is a perspective view showing an arrangement of channels formedwithin a light guide ribbon structure according to the presentinvention;

FIG. 10 is a perspective view of a light guide ribbon structure;

FIG. 11 is a schematic block diagram showing a manufacturing processused to fill channels with an optical material for forming light guides;

FIG. 12 is a schematic block diagram showing an alternate manufacturingprocess used to fill channels with an optical material for forming lightguides;

FIG. 13 is a perspective, exploded view showing a stacking of individuallight guide ribbon structures;

FIG. 14 is a perspective view of a portion of an assembled opticalconverter using stacked light guide ribbon structures;

FIGS. 15 a, 15 b, 15 c, and 15 d show, in a sequence, the fabrication ofan optical converter using stacked light guide ribbon structures withthe addition of optional spacers;

FIG. 16 is a perspective view of a light guide ribbon structure foldedagainst itself to form an optical converter according to one embodimentof the present invention;

FIG. 17 is a side view showing an alternate method for accordion-foldinga sheet of light guide ribbon structures for forming an opticalconverter;

FIG. 18 is a perspective view showing how a light guide ribbon structurecan be adapted to provide a curved surface;

FIG. 19 shows an alternate embodiment in which a light guide ribbonstructure has more than one input edge, routing light guides to anoutput edge;

FIG. 20 is a cross-sectional view showing an optional method forproviding light guides that operate by reflection; and,

FIG. 21 is a perspective view showing a portion of a multilayer lightguide ribbon structure in an alternate embodiment.

FIG. 22 shows an assembly cross section view of another embodiment of anoptical converter.

FIG. 23 shows a view of the embodiment of FIG. 22 assembled and in crosssection.

FIG. 24 shows a top view of a substrate having light guides inaccordance with one embodiment of the invention.

FIG. 25 shows a face view of a substrate of FIG. 24

FIG. 26 shows the formation of channels on the substrate of FIGS. 24 and25.

DETAILED DESCRIPTION OF THE INVENTION

The present description is directed in particular to elements formingpart of, or cooperating more directly with, apparatus in accordance withthe invention. It is to be understood that elements not specificallyshown or described may take various forms well known to those skilled inthe art.

Substrate Formation

The medium of the present invention is formed using a substrate having apattern of raised areas and channels. FIGS. 1 and 2 show alternativeembodiments for the formation of such a substrate.

FIG. 1 shows a schematic illustration of an overall arrangement of oneembodiment of an extrusion roll molding apparatus 20 for fabricating asubstrate 22. In this embodiment, an extruder 24 provides athermoplastic material 26, such as a polymer, onto a base 28 that can beformed from the same material as thermoplastic material 26 or that canbe formed from different materials such as papers, films, fabrics orother useful base materials. Base 28 is fed from a base supply roll 30.Thermoplastic material 26 and base 28 pass into a nip area 32 between asupport 33 shown in FIG. 1 as a pressure roller 34 and a pattern roller36. As thermoplastic material 26 passes through nip area 32, support 33and pattern roller 36 press the thermoplastic material 26 onto base 28and a roller pattern 38 of raised surfaces and channels (not shown) onpattern roller 36 is impressed into thermoplastic material 26. Whenroller pattern 38 is impressed into thermoplastic material 26 some ofthe melted thermoplastic material 26 fills channels (not shown) inroller pattern 38 to form raised areas (not shown) on a patternedsurface 42 of substrate 22 and the balance of thermoplastic material 26is squeezed onto base 28 forming channels (not shown). Accordingly, thisforms a channel pattern 40 having channels separated by raised areas ona patterned surface 42 of thermoplastic material 26. The arrangement ofraised areas and channels in channel pattern 40 is the negative of thearrangement of raised areas and channels found on roller pattern 38.Thermoplastic material 26 is then cooled below a melting temperature ofthermoplastic material 26 or otherwise cured and substrate 22 is thenwound onto a substrate take up roll 44 for further processing as will bedescribed in greater detail below.

FIG. 2 shows another embodiment of an extrusion roll molding apparatus20 that can be used to form substrate 22. In the embodiment of FIG. 2,extrusion roll molding apparatus 20 comprises an extruder 24 that meltsthermoplastic material 26. Melted thermoplastic material 26 supplied byextruder 24 is pressed into nip area 32 between support 33 and patternroller 36. Melted thermoplastic material 26 passes material betweensupport 33 and pattern roller 36 and is cooled below the meltingtemperature of thermoplastic material 26 to form substrate 22. As meltedthermoplastic material 26 is passed through nip area 32 to formsubstrate 22, a roller pattern 38 on pattern roller 36 is impressed intomelted thermoplastic material 26 to form a channel pattern 40 ofchannels (not shown) separated by raised areas (not shown) on patternedsurface 42 of substrate 22 that is the negative of pattern roller 36.Substrate 22 is then wound onto a substrate take up roll 44 for furtherprocessing as will be described in greater detail below.

In the embodiment shown, pattern roller 36 comprises a metallic rollersuch as chrome, copper or stainless steel into which roller pattern 38is formed. However, in other embodiments, pattern roller 36 can comprisea variety of forms. For example, pattern roller 36 can comprise any typeof dimensionally stable roller, drum, belt or other surface that isadapted so that a metallic plate, sleeve or other structure (not shown)having roller pattern 38 formed thereon that can be joined to patternroller 36 to provide a metallic contact surface having the desiredroller pattern 38. This allows the same pattern roller 36 to be used inconjunction with many different roller patterns simply by changing thesleeve, metallic plate or other structure having roller pattern 38.

Forming roller pattern 38 on a metallic pattern roller 36 or metallicplate, metallic sleeve or other metallic structure that can be joined topattern roller 36, provides protection to the precision geometry ofroller pattern 38, provides excellent mechanical wear properties and isan excellent conductor of heat and pressure. Roller pattern 38 can beformed on pattern roller 36, a plate, sleeve or other structure by knownmachining techniques, including but not limited to, techniques such asmachining the desired pattern directly into the roller surface utilizingwire electrical discharge machining tools, etching the pattern directlyinto the roller, growing the pattern by use of photolithography,machining the pattern using high energy lasers, diamond milling, ionbeam milling or creation of a random pattern by bead blasting the rollerfollowed by chrome plating.

In alternative embodiments, pattern roller 36 or a plate, sleeve orother structure bearing roller pattern 38 can be formed using othernon-metallic materials. For example pattern roller 36 can be formed frommaterials such as ceramics or certain plastics. Roller pattern 38 can beformed in such materials using known techniques including, but notlimited to, casting, oblation, ion beam milling, printing andlithographic techniques such as gray scale lithography.

In another alternative embodiment, support 33 can take other forms suchas a belt, platen or other structure capable of providing sufficientsupport so that pattern roller 36 can be impressed into thermoplasticmaterial 26 to form channel pattern 40. Similarly, the pattern roller 36can also alternatively comprise other structures such as a belt, areciprocating belt system or other movable surface onto which a rollerpattern can be formed.

FIGS. 3 and 4 show, respectively, a perspective and cross-section viewof an example of substrate 22 formed in accordance with the embodimentof FIG. 1. FIG. 3 shows an example of channel pattern 40 formed onpatterned surface 42 of substrate 22 by roller pattern 38. As can beseen in FIG. 3, channel pattern 40 can comprise various shapes, sizesand arrangements intended to facilitate particular electrical, magnetic,mechanical, optical or chemical structures as will be described ingreater detail below. Raised areas 52 and channels 54 define each shape.FIG. 3 shows examples of only a few of the possible shapes that can beformed on a patterned surface 42 of substrate 22. Other shapes includeordered arrays of triangles, continuous fluidic channels, pyramids,squares, rounded features, curved features, cylinders, and complexshapes with multiple sides. In certain embodiments, the separationbetween raised areas 52 and channels 54 can range from 0.1 micrometersto about 100 micrometers, however, in other embodiments the sizes of theseparation can range between 0.5 micrometers and 200 micrometers. It hasexperimentally been found that such extrusion roll molding processesprovides precision negative replication of roller pattern 38. Forexample, it has been shown that where extrusion roll molding is used toform channel pattern 40 on patterned surface 42 of substrate 22, thefeatures of channel pattern 40 typically replicate the dimensions of thefeatures of roller pattern 38 at greater than 95% of the dimensionalrange. Such precision formation is possible even when forming substrate22 operating at machine speeds in the 20 to 200 meter/min range.Accordingly, it is possible to reliably and economically form precisearrangements of raised areas 52 and channels 54 in substrate 22. Thisallows substrate 22 to be used to define a platform for fabricating andassembling a wide variety of useful structures.

Thermoplastic material 26 can comprise a variety of suitable materials.For example, polymers are generally low in cost, and can be efficientlyformed into subsequent shapes utilizing known processes such as meltextrusion, vacuum forming and injection molding. Example polymers thatcan be used for thermoplastic material 26 include polyolefins,cyclo-olefins, polyesters, polyamides, polycarbonates, cellulosicesters, polystyrene, polyvinyl resins, polysulfonamides, polyethers,polyimides, polyvinylidene fluoride, polyurethanes,polyphenylenesulfides, polytetrafluoroethylene, polyacetals,polysulfonates, polyester ionomers, and polyolefin ionomers. Copolymersand/or mixtures of these polymers to can be used to obtain athermoplastic material 26 having specific mechanical or opticalproperties. Polyamides that can be used in thermoplastic material 26include, but are not limited to, nylon 6, nylon 66, and mixturesthereof. Copolymers of polyamides are also suitable continuous phasepolymers that can be used in thermoplastic material 26. An example of auseful polycarbonate is bisphenol-A polycarbonate. Cellulosic esters arealso suitable for use as thermoplastic material 26 and include cellulosenitrate, cellulose triacetate, cellulose diacetate, cellulose acetatepropionate, cellulose acetate butyrate, and mixtures or copolymersthereof. Polyvinyl resins that can be used in thermoplastic material 26include polyvinyl chloride, poly(vinyl acetal), and mixtures thereof.Copolymers of vinyl resins can also be utilized.

In addition, thermoplastic material 26 can comprise various knownpolyesters for the polymer features of the invention including thoseproduced from aromatic, aliphatic or cycloaliphatic dicarboxylic acidsof 4–20 carbon atoms and aliphatic or alicyclic glycols having from 2–24carbon atoms. Examples of suitable dicarboxylic acids include, but arenot limited to, terephthalic, isophthalic, phthalic, naphthalenedicarboxylic acid, succinic, glutaric, adipic, azelaic, sebacic,fumaric, maleic, itaconic, 1,4-cyclohexanedicarboxylic,sodiosulfoisophthalic and mixtures thereof. Examples of suitable glycolsinclude, but are not limited to, ethylene glycol, propylene glycol,butanediol, pentanediol, hexanediol, 1,4-cyclohexanedimethanol,diethylene glycol, other polyethylene glycols and mixtures thereof.

Addenda is optionally added to thermoplastic material 26 to improve theoptical, mechanical, chemical, magnetic or electrical characteristics ofchannel pattern 40 of raised area 52 and channel 54 formed inthermoplastic material 26. An example of such useful addenda that can beadded include, but are not limited to, an optical brightener. An opticalbrightener is substantially colorless, fluorescent, organic compoundthat absorbs ultraviolet light and emits it as visible blue light.Examples include, but are not limited to, derivatives of4,4′-diaminostilbene-2,2′-disulfonic acid, coumarin derivatives such as4-methyl-7-diethylaminocoumarin, 1–4-Bis (O-Cyanostyryl) Benzol and2-Amino-4-Methyl Phenol. Other useful addenda that can be added tothermoplastic material 26 include antistatic compounds, pigments, dyes,carbon black, polymer stabilizers or ultraviolet absorbers. Blackthermoplastic can enhance the contrast of the waveguided image.

As is described above, substrate 22 has a patterned surface 42 with achannel pattern 40 formed by contact with roller pattern 38. As is shownin FIG. 4, substrate 22 also has a base surface 46 on a side ofsubstrate 22 that is opposite from patterned surface 42. In certainembodiments, base surface 46 can be formed to receive image formingmaterials such as inks, dyes, toners, and colorants. This permits imagesto be formed, for example, on base surface 46 using ink jet printing,thermal printing, contact press printing and other techniques. There arevarious ways in which this can be done.

Where substrate 22 is formed using the extrusion roll molding apparatus20 described in FIG. 1, base surface 46 is a surface that is a componentof base 28. Accordingly, base 28 can be formed from a material that isadapted to receive image forming materials. Alternatively, base 28 canalso be formed from a material that forms images when exposed to energysuch as thermal, electrical, optical, electromagnetic or other forms ofenergy. Similarly, where substrate 22 is formed using the extrusion rollmolding apparatus described in FIG. 2, base surface 46 is formed fromthermoplastic material 26. Accordingly, in such an embodiment, athermoplastic material 26 can be used that is capable of receiving imageforming materials or that is capable of forming an image when exposed toenergy. In still another alternative embodiment, base surface 46 can beadapted by chemical or other treatments or coatings to receive imageforming materials or to form images when exposed to energy.

In the embodiment shown in FIGS. 3 and 4, substrate 22 has a thicknessbetween base surface 46 and channels 54 of approximately 100 microns.This provides rigidity and structure to substrate 22 that enableschannel pattern 40 to maintain dimensional stability. However, incertain applications, channel pattern 40 can contain one or morechannels 54 that are separated from base surface 46 to a differentdegree and can form a passage through substrate 22 and define an openingat base surface 46.

Channel pattern 40 formed on substrate 22 can also optionally be coatedwith coatings that improve the optical, physical, electrical or chemicalcharacteristics of raised areas 52 and channels 54. Examples of suchcoatings include urethane for scratch resistance, hard coats, antiglarecoatings, antireflection coatings, antistatic materials and dyes forchanging the color of the polymer features. Coating methods that can beused to apply such coatings include, but are not limited to, rollcoating, slit die coating, gravure coating, curtain coating, and ink jetcoating. Such coatings can be applied in a uniform, random or controlledpattern. Coatings can also form cladding, typically a layer with arelatively low index of refraction.

Using Substrate to Form an Optical Converter

Referring to FIG. 5, there is shown a representative light guide ribbonstructure 80 which serves as an elemental component for opticalconverter fabrication. Formed using substrate 22, light guide ribbonstructure 80 comprises a plurality of light guides 70, generallydisposed in parallel to each other. Light guides 70 extend from an inputedge 86, over width W, to an output edge 88. Adjacent light guides 70 oninput edge 86 are spaced apart by an input edge guide-to-guide distanceI. Depending on how light guides 70 are clustered, a group of lightguides 82, as indicated by a dotted box in FIG. 5, can be furtherseparated at input edge 86 by an input edge guide-to-guide groupdistance I_(g). Adjacent light guides 70 on output edge 88 are spacedapart by an output edge guide-to-guide distance O. To form an opticalconverter having useful optical qualities, it is important to be able toprecisely arrange and geometrically define light guides 70.

Using any embodiment of extrusion roll molding apparatus 20, it ispossible to create a web 74 of substrate 22 with a plurality of channelpatterns 40 thereon having precise arrangements of raised areas 52 andchannels 54. The precise arrangement of raised areas 52 and channels 54can be used to form precise arrangements of light guides 70. One exampleof such a substrate 22 is the web 74 of substrate 22 shown in FIG. 6. Ascan be seen from FIG. 6, channels 54 formed in substrate 22 effectivelyserve as molds that can receive the subsequent application of an opticalmaterial (not shown) to form each light guide 70. The optical materialcan be applied in any of a variety of manners to fill the channels 54.After filling and curing in channels 54 light guides 70 are formed inchannels 54. After formation of each light guide 70, in the channels 54of substrate 22, the web of substrate 22 and light guides 70 formed inthe channels 54 thereon can be divided, for example, by slitting the webof substrate 22 and light guides formed thereon along dotted input edgecut lines C_(i) and output edge cut lines C_(o) shown in FIG. 6, toprovide a plurality of separate light guide ribbon structures 80 a, 80b, 80 c, 80 d and 80 e.

The use of injection roll molding allows a number of alternative channelpatterns 40 to be fabricated in substrate 22. Thus, while FIG. 6 showschannels 54 formed generally parallel to the edges of the sheet ofsubstrate 22, (that is, in a direction parallel to the direction ofsubstrate 22 through extrusion roll molding apparatus 20), otherarrangements are possible. For example, channels 54 can be formed in adirection orthogonal to the edges of substrate 22, as is shown in FIG.7, or at some other angle relative to the edges. Further, the use ofextrusion roll molding methods to form substrate 22 permits theformation of a web 74 of substrate 22 having a length that can be on theorder of several meters or more, and which could extend a thousandmeters or more. This permits economical bulk fabrication of, forexample, light guide ribbon structures 80 using such a web 74 ofsubstrate 22.

As is shown in FIG. 8, raised areas 52 and channels 54 can have a rangeof possible cross-sectional shapes, as determined by roller pattern 38on pattern roller 36 with these cross sectional shapes adapted toreceive a curable optical material 90 and to mold curable opticalmaterial 90 to form light guides 70 a, 70 b and 70 c having shapes thatconform to shapes of channels 54. Further, as is shown in FIG. 9, thepath taken by individual ones of light guides 70 a, 70 b, and 70 c froman input edge 86 of light guide ribbon structure 80 to an output edge 88can vary. For example, direct light guides 70 a can be provided thatmove light across a direct path between a input edge 86 and output edge88, indirect light guides 70 b can be provided that move light across aless direct path, and circuitous light guides 70 c can also be providedthat move light along a more circuitous route.

In addition, fabrication using any embodiment of the extrusion rollmolding apparatus 20 allows the dimensions of channels 54 to becontrolled at different locations along light guide 70, thus allowinglight guide 70 to have different cross-sectional areas and/or shapesalong its length. For example, as is shown in FIG. 10, a light guideribbon structure 80 has light guides 70 each having an exit area A₂ nearoutput edge 88 that is larger than an entrance area A₁ of light guides70 at the input edge 86. This can be used for example, in conjunctionwith one or more picture elements of a video display to improve theeffective pixel fill factor or to adjust the brightness of the display.This capability could also be used, for example, for forming theequivalent of a tapered optical fiber faceplate, such as fiber optictapers available from Edmund Industrial Optics, Barrington, N.J. In atapered optical fiber faceplate, each composite optical fiber is widerat one end than at the other.

Application of Optical Material for Forming Light Guides

As noted above, light guides 70 are formed using substrate 22 byapplying an optical material 90 to fill or partially fill channels 54 insubstrate 22. Optical material 90 is typically some type of transmissivematerial having favorable optical qualities for light transmission andrefraction. For example, optical material 90 could be a polymer of thetype that can be cured as a result of exposure to ultra-violet light,such as Norland Optical Adhesive from Norland Products, Cranbury, N.J.Alternate types of optical material 90 can be utilized, depending onspeed, temperature, thickness, flexibility and other requirements.

Substrate 22 surrounds the optical material 90 and has an index ofrefraction that is less than the index of refraction of the substrate22. Such an arrangement typically results in substantial internalreflection of light traveling through the optical material 90. Theinternal reflection of light occurs when light traveling down theoptical is reflected back towards the center of the optical material asthe light encounters the inner surface of the substrate 22. Theefficiency of the optical waveguide decreases if the substrate 22 issmaller in index of refraction than the optical material 90 by less than0.05. The substrate 22 could have, in another embodiment, a layer ofcladding between the substrate and the optical material. This allowsmore freedom in the polymer or material chosen for the substrate becausethe cladding has the property of having an index of refraction lowerthan the optical material and produces the waveguiding effect. In someembodiments, cladding (not shown) can be co-extruded with, coated on, ordeposited on substrate 22 adjacent to the light guides to help influencethe index of refraction. The cladding can also be a reflective layer.Having a reflective layer (such as metal) surrounding the opticalmaterial acts like a mirror and keeps most of the light in the opticalmaterial making a very efficient waveguide.

A variety of materials can be used to form optical material 90 andcladding. Optical material 90 is typically formed from a polymericmaterial, including, for example methacrylates, such as n-butylmethacrylate and 2-ethylhexyl methacrylate. In particular, one suitableoptical material includes a 1:1 mixture by weight of n-butylmethacrylate and 2-ethylhexyl methacrylate, which, in turn, can contain0.05% by weight triethylene glycol dimethacrylate crosslinking agent and0.2% by weight di(4-t-butylcyclohexyl)peroxydicarbonate (Perkadox16.TM., Akzo Nobel Chemicals, Inc., Chicago, Ill.) thermal initiator.Additional materials and examples are presented in U.S. Pat. No.5,225,166, incorporated herein by reference.

Cladding can be formed from a variety of different compounds. Polymersare preferred as they are cheap and easily processable. As an example,fluoropolymers have been found to be useful as a cladding for the lightguiding layer because of their relatively low index of refraction. Thelarger the difference in index of refraction (with the optical materialhaving a higher index of refraction than the cladding) the moreefficient the light guide is and less light is lost.

The specific type of optical material 90 then determines the necessarycuring time and needed cure conditions, such as heat or light energy.Optical material 90 is typically applied in an amorphous or other statethat allows optical material to flow into channels 54 and is curable sothat after optical material 90 has filled channels 54, optical material90 can transition into a state that allows optical material 90 tosolidify enough to remain within channels 54 and to provide an efficientand useful optical pathway. In one embodiment, as shown in FIG. 11,optical material 90 is introduced into channels 54 on substrate 22 usingroller pressure. FIG. 11 shows, in schematic form, a coating apparatus94 for forming light guides 70 using web 74 of substrate 22. Websubstrate 22 is formed as described above or using some other method, isfed from a source, such as a roll 96. Alternately, the source cancomprise an extrusion roll molding apparatus 20 used to supply web 74 ofsubstrate 22 directly to coating apparatus 94 without intermediatestorage of web 74 of substrate 22 on roll 96.

In the embodiment shown in FIG. 11, web 74 of substrate 22 is pulledthrough a gap 98 between rollers 100 and 102. A source 104 provides asupply of optical material 90 that flows into gap 98. Rollers 100 and102 apply pressure that forces optical material 90 into channels 54 toform web 106 of light guide ribbon structures with light guides 70 inappropriate channels 54. Web 106 is then wrapped onto a receiver 108 orstored in some other way. Alternately, web 106 can be further processedin-line, optionally coated or otherwise treated, then cut, folded orotherwise processed to provide individual light guide ribbon structures80, ready for use in forming an optical converter.

Referring to FIG. 12, there is shown another embodiment of a coatingapparatus 94 that uses a slightly different technique for fillingchannels 54 in substrate 22. Here, web 74 of substrate 22 is passedbetween coating support 112 and a skiving mechanism 114 that iscontinuously supplied by source of optical material 90 with a meniscus116 of optical material 90. This forces optical material 90 intochannels 54, forming light guides 70 within channels 54 as web 106 isfed forward and onto receiver roll 108.

Any of a number of other coating techniques known in the art can be usedto apply optical material 90 to fill or partially fill channels 54 insubstrate 22. Specific examples of such other methods include: rollcoating and doctor blade coating, gap coating, curtain coating, slot diecoating, spraying or printing or using and other coating techniques,some of which are described in greater detail below. Certain of thesecoating methods are described in greater detail in commonly assignedU.S. patent application Ser. No. 10/411,624 filed Apr. 11, 2003, in thename of Kerr et al.

Various types of additional coatings can optionally be provided forduring light guide ribbon structure 80 fabrication, either before orafter filling channels 54 with optical material 90. For example, opticalcoatings could be applied for optimizing reflective response, forimproved light absorption, to provide a different index of refraction,or for reducing stray light effects. Other types of coatings could beapplied, including protective or adhesive coatings, for example, orcoatings that provide spacing distances or suitable mounting surfaces.Coatings could be applied to either or both sides of substrate 22, or toany portion thereof, including channels 54 or surrounding structures.For example, a coating could be applied only within one or more channels54, to provide channels 54 having specific optical properties. Coatingsfor spacing could be applied at appropriate thicknesses for obtainingthe needed distance between adjacent rows of light guides 70 at inputand output edges 86 and 88. It would be possible, for example, to varythe coating thickness appropriately between input and output edges 86and 88 in order to obtain the necessary dimensions. In one embodiment,an output-to-input thickness ratio for an applied coating exceeds about1.4, for example.

Assembly and Alignment

Referring to FIGS. 13 and 14, there are shown exploded and assembledviews, respectively, that illustrate how light guide ribbon structures80 a, 80 b, 80 c and 80 d can be stacked together in order to form anoptical converter 120 having an input edge 122 and an output edge 124.In another alternative, light guide ribbon structures 80 a, 80 b, 80 cand 80 d can have predefined mounting and/or alignment passages 128 thatallow mechanical locating structures such as an alignment pin 130 to beinserted into alignment passages 128. Such alignment passages can beformed as a part of the pattern of channels 40 formed on substrate 22.Other conventional mechanical alignment mechanisms can be used. Othermechanisms for obtaining alignment between light guide ribbon structures80 could include for example, holes, detents, sockets, pins, and thelike, for example. Magnets and ferrous materials could alternately beemployed, as part of substrate 22, for example, for obtaining andmaintaining alignment.

Alternatively, light guide ribbon structures 80 a, 80 b, 80 c and 80 dhave output edges 126 a, 126 b, 126 c, and 126 d respectively that areused for aligning the light guide ribbon structures 80 a, 80 b, 80 c and80 d. For example, the alignment of output edges 126 can be accomplishedusing an external jig or form (not shown) to engage output edges 126 toensure proper alignment.

Electromechanical systems can also be used. For example, machine visionor other like sensing systems can be used to determine alignment of aplurality of light guide ribbon structures, electronically, based uponthe appearance of the arrangement of light guide ribbon structures andto mechanically adjust the same based upon the sensed information

Light guide ribbon structures 80 a, 80 b, 80 c and 80 d can be affixedto each other using an adhesive, for example. An adhesive could becoated onto light guide ribbon structure 80 during fabrication, allowing“peel-and-stick” adhesion of ribbon structures 80 to each other or tosome other surface. Optionally, an adhesive could be applied duringassembly of optical converter 120. Fillers and spacer elements couldalso be provided. Alternate ways for joining light guide ribbonstructures 80 a, 80 b, 80 c and 80 d include using mechanical fasteners,thermal stoking, welding, compression fitting and/or forminginterlocking features on each of light guide ribbon structures 80 a, 80b, 80 c and 80 d that are adapted to engage like features on adjacentlight guide ribbon structuring. Any other known mechanical system can beused to join light guide ribbon structures 80 a, 80 b, 80 c and 80 d inan aligned fashion.

In FIGS. 13 and 14, light guide ribbon structures are shown as beingaligned by being stack in a predefined linear stacking pattern. However,other stacking patterns can be used.

FIGS. 15 a through 15 d show side views of one embodiment depictingsuccessive light guide ribbon structures 80 can be stacked against eachother to form an optical converter 120. FIG. 15 a shows a single lightguide ribbon structure 80, having added input and output edge spacers142 and 144 respectively. FIG. 15 b shows multiple light guide ribbonstructures 80 lined up symmetrically, with input edge spacer 142 andoutput edge spacer 144 having the proper orientation for stacking. FIG.15 c shows how output edge 148 is assembled, with output edge spacers144 disposed between light guide ribbon structures 80. FIG. 15 d showshow input edge 146, represented by a dotted line, is then formed. Assuggested in FIG. 15 d, some trimming at input edge 146 may be requiredfor maintaining flatness at input edge 146. Of course, light guideribbon structures 80 can be fabricated to have different widths (W inFIG. 1), thereby obviating the need for trimming as suggested in FIG. 15d.

Where used, input edge spacer 142 maintains the fixed input edgeguide-to-guide distance I_(g) and also determines an input edge distancebetween light guide ribbon structures 80 when stacked, as is describedsubsequently. As is noted above, a collection of light guides may formgroup of light guides 70; with such an arrangement, there would be aninput edge guide-to-guide group distance I_(g) between groups of lightguides 70 at input edge 146. Similarly, light guide ribbon structures 80on output edge 148 have an output edge guide-to-guide distance O. Outputedge spacer 144 maintains the fixed output edge guide-to-guide distanceO and also determines an output edge distance between successive lightguide ribbon structures 80 when stacked against each other, as isdescribed subsequently.

Input edge spacer 142 and output edge spacer 144 could be fabricatedfrom a number of different materials and could be tape, plastic,adhesive, or molded, for example. Alternately, light guide ribbonstructure 80 itself could be fabricated to be thicker or thinner ateither input edge 146 or output edge 148, thereby providing the properdimensional relationship when stacking. Or, coatings could be employedto achieve separation at suitable spacings for input edge 146 and outputedge 148. For example, a coating having a variable thickness can be usedsuch as a coating that is thicker along output edge 148 than along inputedge 146. Where such coatings are used to obtain separation at inputedge 146 and output edge 148, the ratio of coating thickness alongoutput edge 48 to coating thickness along input edge 146 can be, forexample, in excess of about 1.4.

Referring to the perspective view of FIG. 16, there is illustrated analternate embodiment of a method for assembling optical converter 120.In this embodiment a web 106 of light guide ribbon structures 80 isfolded back against itself one or more times on fold lines F. Referringto FIG. 17, there is illustrated yet another embodiment of a method forassembling optical converter 120 from slits 150 of ribbon structures 80.In this embodiment, slits 150 is accordion-folded at positionscorresponding to the input edge cut lines C_(i) and output edge cutlines C_(o) shown in FIG. 6. Optional input and output edge spacers 142and 144 can be inserted into the accordion-folded stack 152, asindicated in FIG. 17. The folding arrangements of FIGS. 16 and 17 allowsimilar alignment mechanisms as are noted above for use with individualstacked light guide ribbon structure 80 segments.

Shaping Optical Converter 120

The use of light guide ribbon structures 80 allows considerableflexibility for adapting the dimensions and curvature of opticalconverter 120. By changing the length of light guide ribbon structure 80segments, various arrangements of height and width for optical converter120 can be obtained. Light guide ribbon structures 80 can be wrappedtogether in a number of different ways to adapt the shape of opticalconverter 120, for example. As is noted above, light guide ribbonstructures 80 themselves could be fabricated with curved shapes,allowing a variety of shaped arrangements for optical converter 120.

Slight adaptations at input and output edges 146 and 148 can allow lightguide ribbon structures 80 to be combined to provide a curvature to aninput edge 122 or an output edge 124 of optical converter 120. Referringto FIG. 18, light guide ribbon structure 80 is adapted for a slightcurvature Q with a number of slits 150 in input edge 146 and output edge148 to yield curvature Q as shown. Curvature Q could be in either aconvex or concave direction. Curvature Q could be provided as ribbonstructure 80 is formed on substrate 22 or could be provided bysubsequent processes, such as providing slits 150 as shown in FIG. 18. Avariety of additional shapes and arrangements can be obtained, includingarrangements having a different number of input edges 146 and outputedges 148. FIG. 19 shows a simple example in which a light guide ribbonstructure 80 has more than one input edge 146, routing light guides 70to output edge 148. Using a combination of curvature, variousarrangements of input and output edges 146 and 148, and tiling, largedisplay structures could be assembled from optical converters 120fabricated according to the present invention.

Finishing Operations

Once light guide ribbon structures 80 are appropriately aligned so as toform input face 122 and output face 124, finishing operations can beperformed. These processes provide final shaping, encasing materials,and surface finishing operations, and may also employ methods forimproving the optical performance of assembled optical converter 120.

Heat or abrasive substances may be employed for shaping the ends oflight guides 70. For example, heat may be applied to shape the end ofeach light guide 70, forming an integral lens structure for each channel54 thereby.

Any number of types of interstitial substances can be used for fillingspaces between light guide ribbon structures 80. Interstitial materialsmay comprise plastics, resins, epoxies, or other suitable materials,including materials selected for specific optical properties, such asfor light guiding. Black interstitial material, or interstitial materialhaving a specific optical index could be employed to preventing unwantedeffects, such as cross-talk between light guide ribbon structures 80.Optical converter 120 can be finished by immersion into a hardeningliquid of some type.

It must be noted that interstitial substances would be optional, sincethere may be uses for which a flexible optical converter 120 arrangementis most advantageous. For example, there may be applications in whichdithering or other mechanical movement or flexibility is useful.

Methods for Obtaining Alignment of Pixels

One key problem in optical converter fabrication relates to fiberalignment to individual light sources in an array or “pixel-to-pixel”alignment. This problem has not been satisfactorily solved forhigh-density imaging applications using the conventional fabricationmethods described in the background material above. Instead, some typeof workaround has been used, such as generally grouping multiple opticalfibers for a single light source so that at least some of the fibersreceive the intended light. However, such a solution does not providepixel-to-pixel alignment and clearly constrains the resolution ofoptical converter 120.

Using the method of the present invention allows for the formation of anoptical converter 120 having a precise arrangement of light guides 70.In particular, the arrangement of light guides 70 within each lightguide ribbon structure 80 can be precisely defined and shaped withineach light guide ribbon structure 80. Further, using the method of thepresent invention, the relative arrangement of light guides 70 in onelight guide ribbon structure 80 can be precisely positioned relative tothe arrangement of light guides 70 in an adjacent light guide ribbonstructure 80. The degree of optical conversion can be precisely definedin a bi-axial manner with the degree of conversion provided across thelight guides 70 of individual light guide ribbon structures beingdifferent from the degree of conversion provided between light guideribbon structures 80 of the optical converter 120.

It is instructive to note that the terms “input” and “output” as used inthis specification are relative terms and could be reversed. The sensein which these terms are used herein relates to use of optical converter120 as part of a display, including a tiled display, for example.Optical converter 120 could alternately be used as part of alight-gathering instrument, in which case the input side would typicallyrequire larger guide-to-guide spacing I to direct light to a smallsensing component on output face 124. The method of the presentinvention allows fabrication of fiber optic faceplates 100 used ineither orientation, with variable spacing at opposite faces or withequal spacing if needed.

Alternate Embodiments

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the scope of theinvention as described above, and as noted in the appended claims, by aperson of ordinary skill in the art without departing from the scope ofthe invention. For example, optical converter 120 componentsmanufactured using the methods and apparatus of the present inventioncould be any of a range of sizes. Various methods could be applied forfinishing, packaging, and tiling optical converters 120 that have beenfabricated using the methods and apparatus of the present invention.Light guide ribbon structures 80 are preferably fabricated assubstantially flat ribbons for ease of stacking. However, secondaryoperations such as vacuum forming could be employed for further shapingof light guide ribbon structures 80.

In the preferred embodiment described above, light guides 70 areprovided only on one side of substrate 22. However, light guides 70could alternately be provided on both sides of substrate 22 and could bealigned or staggered in a number of different configurations on eitherside. The embodiment shown in FIGS. 11, 12, 13, 14 and 15 a through 15 dforms and uses light guide ribbon structure 80 in a configurationwherein a single row of light guides 70 is provided. However, the samebasic process described for forming light guide ribbon structure 80could be repeated one or more times to build up a multi layer lightguide ribbon structure 160 having a row of light guides 70 in eachlayer. FIG. 20 shows a multilayer light guide ribbon structure 160having two layers 162 a and 162 b. Layer 162 b is initially formed ontosubstrate 22, using the methods described above. Layer 162 a is thenformed using either a second layer of substrate 22, as shown in FIG. 20,or using an intermediate layer that is coated onto layer 162 b, forexample. It will be appreciated that an optical converter 120 can beformed using such multilayer light guide ribbon structure 160. This canbe done by assembling more than one multilayer guide ribbon structure160 using the techniques described for assembling light guide ribbonstructure 80 to form an optical converter 120.

Alternatively, the process of assembling light guide ribbon structures80 to form an optical converter 120 can be performed by forming aninitial web layer of light guide ribbon structures by the steps of rollmolding a web of substrate having a pattern of channels each channelspaced apart from its adjacent channel in accordance with a predefinedpattern and coating an optical material into the channels on the web ofsubstrate to form light guides and forming at least one subsequent weblayer of light guide ribbon structure 80 on the initial web layer 80 bythe steps of roll molding a web of substrate on the initial web layer oflight guide ribbon structures, with each subsequent layer having apattern of channels, each channel spaced apart from its adjacent channelin accordance with a predefined pattern and coating an optical materialinto the channels on the web of substrate to form light guides. A webthus formed can then be segmented to form an optical converter having aninput edge and an output edge with an array of stacked light guidesextending therebetween.

In the embodiments described hereinabove, light guides 70 are describedas being formed using optical material 90. Another option is to form oneor more reflective light guides 170 in the form of a reflective tube asis shown in the cross-sectional view of FIG. 21. For such anarrangement, one or more channels 54 would be formed and given areflective coating 172. An optional reflective coating 174 can then beprovided as a covering to provide a reflective surface with a reflectivelight guide 70 constructed in this manner.

Still another embodiment of this type is shown in FIGS. 22 and 23 thatshow an optical converter 120 that is formed by joining at least twolight guide ribbon cables 176 and 178. As is shown in the FIG. 22, lightguide ribbon cables 176 and 178 each have a patterned surface 42 and apatterned base surface 46 having channels 182 and 184 respectivelyformed therein. Each of these light guides has a reflective cladding 180coated or otherwise provided along channels 182 and 184 to form areflective surface. In this embodiment, channels 182 and 184 are adaptedto cooperate to form light guides 70 when a first light guide ribboncable 176 and second light guide ribbon cable 178 are joined together.In this embodiment, each light guide ribbon cable 176 and 178 have apatterned surface 42 with an alignment surface 186 and a patterned basesurface 46 having an alignment channel 188 adapted to receive alignmentsurface 186 and to facilitate alignment of each light guide ribbon cable176 and 178 with respect to each other. In this embodiment, channels 182and 184 can be formed on base surface 46 by forming a pattern on support33 shown in FIG. 1 as a pressure roller 34. However, such a pattern cansimilarly be formed on an alternate embodiment of support 33. Althoughonly one such alignment surface 186 and one such alignment channel areshown on each surface, patterns of more than one can be used.

It will be appreciated that in yet another alternative embodiment,extrusion roll molding apparatus 20 of FIG. 2 can be used to directlyform light guides 70 on substrate 22 by reversing the process describedabove and applying a pattern of optical material 90 to a base 28 usingthe process described above for applying thermoplastic material 26 tobase 28. This forms light guides 70 directly on substrate 22. A top viewand cross-section view of such a substrate is shown in FIGS. 24 and 25.It will also be appreciated that, in this embodiment, a thermoplasticmaterial 26 or other material can then be applied to the substrate 22formed in this fashion using the coating techniques described herein orotherwise known in the art to apply a coating of a thermoplasticmaterial 26 to form channels 54 and a light guide ribbon structure 80 asshown in FIG. 26.

Therefore, what is provided is an improved apparatus and method forforming an optical converter.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST

-   20 Extrusion roll molding apparatus-   22 substrate-   24 extruder-   26 thermoplastic material-   28 base-   30 base supply roll-   32 nip area-   33 support-   34 pressure roller-   36 pattern roller-   38 roller pattern-   40 channel pattern-   42 patterned surface-   44 substrate take up roll-   46 base surface-   50 pattern-   52 raised area-   54 channel-   70 light guide-   70 a light guide-   70 b light guide-   70 c light guide-   74 web of substrate-   80 light guide ribbon structure-   80 a light guide ribbon structure-   80 b light guide ribbon structure-   80 c light guide ribbon structure-   80 d light guide ribbon structure-   80 e light guide ribbon structure-   82 group of light guides-   86 input edge-   88 output edge-   90 optical material-   94 coating apparatus-   96 roll-   98 gap-   100 roller-   102 roller-   104 source of optical material-   106 web-   108 receiver roll-   112 coating support-   114 skiving mechanism-   116 meniscus-   120 Optical converter-   122 input edge-   124 output edge-   126 a output edges-   126 b output edge-   126 c output edge-   126 d output edge-   128 alignment passages-   130 alignment pin-   142 input edge spacer-   144 output edge spacer-   146 input edge-   148 output edge-   160 slits-   160 multi layer light guide ribbon structure-   162 a ribbon structure layer-   162 b ribbon structure layer-   170 reflective light guides-   172 reflective coating-   174 reflective coating-   176 first light guide ribbon structure-   178 second light guide ribbon structure-   180 reflective cladding-   182 channels-   184 channels-   186 alignment surface-   188 alignment channel-   I_(g) input edge guide to guide group distance-   I input edge guide-to-guide distance-   W width-   O output edge guide to guide distance-   C_(i) input edge cut line-   C₀ output edge cut line-   Q curvature-   A₁ input area-   A₂ output area

1. A method for forming an optical converter comprising: forming a webof light guide ribbon structures by the steps of roll molding a web ofsubstrate having a pattern of channels, each channel spaced apart fromits adjacent channel in accordance with a predefined pattern, andcoating an optical material into the channels on the web of substrate toform light guides; applying a coating to the web of light guide ribbonstructures; segmenting the web of light guide ribbon structures to formindividual light guide ribbon structures with each ribbon structurehaving an input edge and an output edge with light guides extendingtherebetween; and assembling the individual light guide ribbonstructures in a stacked arrangement; wherein said coating applied to thelight guide ribbon structures provides a spacer between adjacent stackedsaid light guide ribbon structures, wherein the optical converter has aninput edge and an output edge and wherein the spacer is used to providea separation between the light guide ribbon structures at the input edgethat is different from the separation of light guide ribbon structuresat the output edge.
 2. The method of claim 1, wherein the ratio of saidoutput edge spacing to said input edge spacing exceeds about 1.4.
 3. Themethod of claim 2, wherein the step of roll molding a substrate having apattern of channels comprises the step of defining a pattern of channelson each side of a substrate.
 4. The method of claim 1, wherein saidlight guide ribbon structures are curved.
 5. The method of claim 1,further comprising the step of shaping an end face of at least one saidlight guides to provide a lens structure.
 6. The method of claim 5,wherein the step of shaping an end face of at least one said lightguides comprises the step of applying heat to said at least one saidlight guides.
 7. A method for forming an optical converter comprising:forming a web of light guide ribbon structures by the steps of rollmolding a web of substrate having a pattern of channels, each channelspaced apart from its adjacent channel in accordance with a predefinedpattern, and coating an optical material into the channels on the web ofsubstrate to form light guides; segmenting the web of light guide ribbonstructures to form individual light guide ribbon structures with eachribbon structure having an input edge and an output edge with lightguides extending therebetween; and assembling the individual light guideribbon structures in a stacked arrangement, wherein a thicknessdimension at said input edge of said substrate differs from a thicknessdimension at said output edge of said substrate.
 8. A method for formingan optical converter comprising: forming a web of light guide ribbonstructures by the steps of roll molding a web of substrate having apattern of channels, each channel spaced apart from its adjacent channelin accordance with a predefined pattern, and coating an optical materialinto the channels on the web of substrate to form light guides;segmenting the web of light guide ribbon structures to form individuallight guide ribbon structures with each ribbon structure having an inputedge and an output edge with light guides extending therebetween; andassembling the individual light guide ribbon structures in a stackedarrangement, wherein at least one said light guide ribbon structure hasa plurality of inputs.
 9. A method for forming an optical convertercomprising: forming a web of light guide ribbon structures by the stepsof roll molding a web of substrate having a pattern of channels, eachchannel spaced apart from its adjacent channel in accordance with apredefined pattern, and coating an optical material into the channels onthe web of substrate to form light guides; segmenting the web of lightguide ribbon structures to form individual light guide ribbon structureswith each ribbon structure having an input edge and an output edge withlight guides extending therebetween; and assembling the individual lightguide ribbon structures in a stacked arrangement, wherein at least onesaid light guide ribbon structure has a plurality of outputs.